Difluoro statone antiviral analogs

ABSTRACT

PCT No. PCT/US94/09053 Sec. 371 Date Feb. 20, 1996 Sec. 102(e) Date Feb. 20, 1996 PCT Filed Aug. 10, 1994 PCT Pub. No. WO95/07257 PCT Pub. Date Mar. 16, 1995The present invention relates to difluorostatone derivatives useful as antiviral agents.

This invention relates to novel statone antiviral analogs, to the processes and intermediates useful for their preparation and to their use as anti-viral agents.

BACKGROUND OF THE PRESENT INVENTION

Retroviruses are a class of viruses which transport their genetic material as ribonucleic acid rather than as deoxyribonucleic acid. Retroviruses are associated with a wide variety of diseases in man, one of which is AIDS. Although there have been disclosures of other anti-viral agents useful in the treatment of AIDS, for example see patent applications EP 0 218 688, EP 0 352 000 and PCT/US 91/09741, the compounds of the present invention have not been previously disclosed. PCT/US 91/09741 is hereby incorporated by reference.

DESCRIPTION OF THE PRESENT INVENTION

More specifically this invention relates to novel difluoro statone analogs of Formula 1 ##STR1## and the stereoisomers, hydrates, isosteres and the pharmaceutically acceptable salts thereof wherein

P₁ is ##STR2## wherein T is (O)_(b) --W--R! and T' is (O)_(b) '--W'--R'! or H, wherein each of W and W' are independently C₁₋₆ alkylene or nothing,

provided that W is C₂₋₆ alkylene when W is directly attached to a nitrogen atom in R, provided that W' is C₂₋₆ alkylene when W' is directly attached to a nitrogen atom in R';

P₂ is C₁₋₆ alkyl, cyclopentyl, hydroxy C₁₋₆ alkyl, phenyl, benzyl or 3-tetrahydrofuryl;

R and R' are each independently C₂₋₆ alkenylene, piperazinyl, substituted piperazinyl, piperidyl, morpholinyl, pyridyl, pyrazinyl, or pyrimidinyl, wherein substituted piperazinyl is piperazinyl substituted on one nitrogen atom thereof with CHO, C(O)NHR₄, C₁₋₄ alkyl or CO₂ R₄ ;

R₁ is benzyloxy, C₁₋₆ alkoxy, C₁₋₆ alkyl, phenyl, benzyl, phenethyl, fluorenylmethylenoxy, 2-quinolinyl, PDL, ##STR3## NHSO₂ R₄, N(R₄) (benzyl), or N(R₄)(PDL); PDL is --(CH₂)_(a) -2-,3-, or 4-pyridyl, or p-substituted benzyloxy, wherein the substitution is with a nitro, OH, amino, C₁₋₆ alkoxy, hydroxy C₁₋₆ alkylene, or halogeno;

R₃ is C₁₋₆ alkenyl, C₁₋₆ alkoxy, hydroxy C₁₋₆ alkyl, C₁₋₆ alkyl, or OH;

R₄ is H, C₁₋₆ alkyl, phenyl or benzyl;

R₅ is H, C₁₋₆ alkyl, OH, C₁₋₆ alkoxy, ##STR4## Y being C₁₋₆ hydroxy alkylene, C₁₋₆ alkyl, or ##STR5## and Z being CHO, CO₂ R₄, CO₂ NHR₄ or ##STR6## and V being OR₄ or hydroxy C₁₋₆ alkylene;

R₆ is as defined for R₅ with the proviso that R₆ is other than H when R₅ is H, and when R₅ and R₆ are taken together with nitrogen atom to which they are attached form a heterocyclic moiety of the formulae ##STR7## R₇ is CH₂ OR₄ or C(O)NHR₄, CHO, R₈ is (H,OH) or =O;

a is zero, 1, 2 or 3;

b and b' are each independently zero or 1;

d and d' are each independently 1 or 2;

e and e' are each independently zero, 1 or 2; and x is zero or one.

Isosteres of the compounds of Formula I include those wherein (a) the α-amino acid residues of the P₁ and P₂ substituents are in their unnatural configuration (when there is a natural configuration) or (b) when the normal peptidic carbamoyl linkage is modified, such as for example, to form ##STR8## (N-methylamide), --COCH₂ -- (keto), --CH(OH)CH₂ -- (hydroxy), --CH(NH₂)CH₂ -- (amino), --CH₂ CH₂ -- (hydrocarbon). Preferably a compound of the invention should not be in an isosteric form. Unless otherwise stated the α-amino acids are preferably in their L-configuration.

A compound of the invention may be in free form, e.g., amphoteric form, or in salt, e.g., acid addition or anionic salt, form. A compound in free form may be converted into a salt form in an art-known manner and vice-versa.

The pharmaceutically acceptable salts of the peptide of Formula I (in the form of water, or oil-soluble or dispersible products) include the conventional non-toxic salts or the quaternary ammonium salts of these peptides, which are formed, e.g., from inorganic or organic acids or bases. Examples of such acid addition salts include acetate, adipate, alginate, aspartate, benzoate, benzenesulfonate, bisulfate, butyrate, citrate, camphorate, camphorsulfonate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, fumarate, glucoheptanoate, glycerophosphate, hemisulfate, heptanoate, hexanoate, hydrochloride, hydrobromide, hydroiodide, 2-hydroxyethanesulfonate, lactate, maleate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, oxalate, paemoate, pectinate, persulfate, 3-phenylpropionate, picrate, pivalate, propionate, succinate, tartrate, thiocyanate, tosylate, and undecanoate. Base salts include ammonium salts, alkalimetal salts such as sodium and potassium salts, alkaline earth metal salts such as calcium and magnesium salts, salts with organic bases such as dicyclohexylamine salts, N-methyl-D-glucamine, and salts with amino acids such as arginine, lysine, and so forth. Also, the basic nitrogen-containing groups may be quaternized with such agents as lower alkyl halides, such as methyl, ethyl, propyl, and butyl chloride, bromides and iodides; dialkyl sulfates like dimethyl, diethyl, dibutyl; and diamyl sulfates, long chain halides such as decyl, lauryl, myristyl and stearyl chlorides, bromides and iodides, aralkyl halides like benzyl and phenethyl bromides and others.

The hydrates of the compounds of Formula I are hydrated compounds having the partial structure ##STR9## and in their end-use application are generally the active forms.

In general, as used herein, the term "alkyl" includes the straight, branched-chain and cyclized manifestations thereof unless otherwise indicated, particularly such moieties as methyl, ethyl, isopropyl, n-butyl, t-butyl, --CH₂ -t-butyl, cyclopropyl, n-propyl, pentyl, cyclopentyl, n-hexyl, cyclohexyl and cyclohexylmethyl. The term "aralkyl", when used, includes those aryl moieties attached to an alkylene bridging moiety, preferably methyl or ethyl.

"Aryl" includes both carbocyclic and hetereocyclic moieties of which phenyl, pyridyl, pyrimidinyl, pyrazinyl, indolyl, indazolyl, furyl and thienyl are of primary interest; these moieties being inclusive of their position isomers such as, for example, 2-, 3-, or 4-pyridyl, 2- or 3-furyl and thienyl, 1-, 2-, or 3-indolyl or the 1- and 3-indazolyl, as well as the dihydro and tetrahydro analogs of the furyl and thienyl moieties. Also included within the term "aryl" are such fused carbocyclic moieties as pentalenyl, indenyl, naphthalenyl, azulenyl, heptalenyl, acenaphthylenyl, fluorenyl, phenalenyl, phenanthrenyl, anthracenyl, acephenanthrylenyl, aceanthrylenyl, triphenylenyl, pyrenyl, chrysenyl and naphthacenyl. Also included within the term "aryl" are such other heterocyclic radicals as 2- or 3-benzo b!thienyl, 2- or 3-naphtho 2,3-b!thienyl, 2- or 3-thianthrenyl, 2H-pyran-3-(or 4- or 5-)yl, 1-isobenzo-furanyl, 2H-chromenyl-3-yl, 2- or 3-phenoxathiinyl, 2- or 3-pyrrolyl, 4- or 3-pyrazolyl, 2-pyrazinyl, 2-pyrimidinyl, 3-pyridazinyl, 2-indolizinyl, 1-isoindolyl, 4H-quinolizin-2-yl, 3-isoquinolyl, 2-quinolyl, 1-phthalazinyl, 1,8-naphthyridinyl, 2-quinoxalinyl, 2-quinazolinyl, 3-cinnolinyl, 2-pteridinyl, 4aH-carbazol-2-yl, 2-carbazolyl, β-carbolin-3-yl, 3-phenanthridinyl, 2-acridinyl, 2-perimidinyl, 1-phenazinyl, 3-isothiazolyl, 2-phenothiazinyl, 3-isoxazolyl, 2-phenoxazinyl, 3-isochromanyl, 7-chromanyl, 2-pyrrolin-3-yl, 2-imidazolidinyl, 2-imidazolin-4-yl, 2-pyrazolidinyl, 3-pyrazolin-3-yl, 2-piperidyl, 2-piperazinyl, 1-indolinyl, 1-isoindolinyl, 3-morpholinyl, benzo b!isoquinolinyl and benzo b!furanyl, including the position isomers thereof except that the heterocyclic moieties cannot be attached directly through their nitrogen one, two or three substituents independently selected from C₁₋₆ alkyl, haloalkyl, alkoxy, thioalkoxy, aminoalkylamino, dialkylamino, hydroxy, halo, mercapto, nitro, carboxaldehide, carboxy, carboalkoxy and carboxamide.

Likewise the term "alkylene" (a divalent alkane radical) includes straight or branched-chain moieties. Some examples of branched-chain alkylene moieties are ethylethylene, 2-methyltrimethylene, 2,2-dimethyltrimethylene, and so on. For example, C₃ alkylene can mean ##STR10##

All (C₁₋₆) moieties such as C₁₋₆ alkyl, C₁₋₆ alkylene, C₂₋₆ alkenylene, C₁₋₆ alkoxy, and hydroxy C₁₋₆ alkyl, are more preferably C₁₋₃ moieties (containing 1-3 carbon atoms instead of 1-6 carbon atoms, more preferably a C₁₋₂ moiety and most preferably a C₁ moiety). "Alkenylene" (divalent unsaturated moiety) can also mean "Alkenyl" such as ethenyl (univalent unsaturated moiety).

The fluorenylmethyloxy moiety is that moiety generally called by its abbreviation FMOC, and is the fluorenyl moiety bearing --CH₂ O attached to the 9-position of the fluoroenyl moiety. Other terms defined herein are piperazinyl ##STR11## or substituted piperazinyl ##STR12## the substitution (★) occurring only at one nitrogen molecule which is not attached to the remainder of the molecule (attachment via a nitrogen atom). The substituents are one of CHO, C(O)NHR₄, C₁₋₄ alkyl or CO₂ R₄.

Piperidyl and morpholinyl both bind to the rest of the ##STR13## molecule via their respective nitrogen atoms while pyrimidinyl, pyridyl and pyrazinyl bind to the rest ##STR14## of the molecule anywhere except their respective nitrogen atoms.

More specifically, in the instance wherein P₂ is either C₁₋₆ alkyl or hydroxy C₁₋₆ alkyl, such moieties as --C(CH₃)₃, --CH(CH₃)₂, --CH(CH₃)(C₂ H₅), --C(OH)(CH₃)₂ and --CH(OH)CH₃ are preferred. The "hydroxy C₁₋₆ alkyl" moiety is illustrated in one example by --CH₂ --OH, the "C₁₋₆ alkoxy C₁₋₆ alkyl" moiety, is illustrated in one example by --CH₂ --OCH₃, (although in each instance the C₁₋₆ alkylene may be straight or branched and the hydroxy radical is not limited to the terminal carbon atom of the alkyl moiety).

As it is often quite advantageous to have what is termed an amino protecting group (Pg), the scope of those compounds of Formula I, includes those R₁ moieties which, together with their adjacent carbonyl moiety form such groups as acetyl (Ac), succinyl (Suc), benzoyl (Bz), t-butyloxycarbonyl (Boc), benzyloxycarbonyl (CBZ), tosyl (Ts), dansyl (DNS), isovaleryl (Iva), methoxysuccinyl (MeOSuc), 1-adamantanesulphonyl (AdSO₂), 1-adamantaneacetyl (AdAc), phenylacetyl, t-butylacetyl (Tba), bis (1-naphthyl)methyl!acetyl (BNMA) and Rz wherein Rz is an aryl group as previously described suitably substituted by 1 to 3 members selected independently from the group consisting of fluoro, chloro, bromo, iodo, trifluoromethyl, hydroxy, alkyl containing from 1 to 6 carbons, alkoxy containing from 1 to 6 carbons, carboxy, alkylcarbonylamino wherein the alkyl group contains 1 to 6 carbons, 5-tetrazolo, and acylsulfonamido (i.e., acylaminosulfonyl and sulfonylaminocarbonyl) containing from 1 to 15 carbons, provided that when the acylsulfonamido contains an aryl. The aryl may be further substituted by a member selected from fluoro, chloro, bromo, iodo and nitro.

In those instances wherein there is an Rz moiety, it is preferred that Rz represent acylsulfonamido, particularly those wherein the acylsulfonamido contains an aryl moiety (preferably phenyl) substituted by a halogen. The preferred Rz moieties being 4- (4-chlorophenyl)sulfonylaminocarbonyl!phenylcarbonyl, 4- (4-bromophenyl)sulfonylamino carbonyl!-phenylcarbonyl and 4- phenylsulfonylamino carbonyl!-phenylcarbonyl (said moieties being abbreviated as 4-Cl-.o slashed.-SAC-Bz, 4-Br-.o slashed.-SAC-Bz and .o slashed.-SAC-Bz, respectively).

Among the classes of amino protecting groups contemplated are: (1) acyl type protecting groups such as formyl, trifluoroacetyl, phthalyl, p-toluenesulfonyl (tosyl), benzenesulfonyl, nitrophenylsulfenyl, tritylsulfenyl, O-nitrophenoxyacetyl, and α-chlorobutyryl; (2) aromatic urethane type protecting groups such as benzyloxycarbonyl and substituted benzyloxycarbonyls such as p-chlorobenzyloxycarbonyl, p-methoxybenzyloxycarbonyl, p-nitrobenzyloxycarbonyl, p-bromobenzyloxycarbonyl, 1-(p-biphenylyl)-1-methylethoxycarbonyl, α-, α-dimethyl-3,5-dimethoxybenzyloxycarbonyl, and benzhydryloxycarbonyl; (3) aliphatic urethane protecting groups such as tert-butyloxycarbonyl (Boc), diisopropylmethoxycarbonyl, iso-propyloxycarbonyl, ethoxycarbonyl, and allyloxycarbonyl; (4) cycloalkyl urethane type protecting groups such as cyclopentyloxycarbonyl, adamantyloxycarbonyl, and cyclohexyloxycarbonyl; (5) thio urethane type protecting groups such as phenylthiocarbonyl; (6) alkyl type protecting groups such as triphenylmethyl (trityl) and benzyl (Bzl); (7) trialkylsilane protecting groups such as trimethylsilane if compatible. The preferred α-amino protecting groups are tert-butyloxycarbonyl (Boc) or benzyloxycarbonyl (CBZ). The use of Boc as an α-amino protecting group for amino acids is described by Bodansky et al. in "The Practice of Peptide Synthesis", Springer-Verlag, Berlin (1984), p. 20.

In general the compounds of this invention may be prepared using standard chemical reactions analogously known in the art.

In the instance wherein it is desired to prepare compounds of the formula ##STR15## wherein R₁, P₂, P₁, R₅ and R₆ are as previously defined, the process outlined by the following reaction schemes may advantageously be utilized. ##STR16##

In effecting reaction scheme A, A' or A", the process is initiated by conducting a Reformatsky-type reaction wherein an aldehyde of Formula (3) is subjected to a condensation reaction with an ester of bromodifluoroacetic acid, preferably the ethyl ester in the presence of zinc and in an anhydrous aprotic solvent, e.g., tetrahydrofuran, ether, dimethoxyethane and the like under a nitrogen or argon inert atmosphere. The reaction is gently heated to about 60° C. for about 1-12 hours or ultrasonicated to produce compounds (4).

Step (b) to obtain compounds (5) or (14) may be effected directly or undirectly. In one instance, the esters of Formula (4) or (13) are de-esterified using a strong base (LiOH, KOH, NaOH and the like) in the presence of water using a partially water miscible solvent (such as tetrahydrofuran, dimethoxyethane, dioxane) at about room temperature. The so-obtained de-esterified compound is then aminated with the appropriate R₅ R₆ -substituted amine using a peptide-like coupling procedure--i.e., using a mixed anhydride method using DCC and hydroxybenzotriazole at room temperature in solvents such as CH₂ Cl₂, tetrahydrofuran or dimethylformamide. Alternatively the esters (4) or (13) may be directly subjected to a reaction with the appropriate R₅ R₆ -substituted amine without or with a solvent (tetrahydrofuran) at about 80° C.

In Step (c) Compounds (6), (8) or (11) are prepared by removal of the P"₁ protecting group using standard procedures, e.g., hydrogenation. The free phenol functionality is then reacted with an appropriate alkyl halide in an inert solvent (preferably anhydrous dioxane or anhydrous dimethylformamide) in the presence of a base (potassium or cesium carbonate) with or without potassium iodide at room or reflux temperature.

In Step (c1) compound (13) is prepared by removal of the P"₁ protecting group using standard procedures, e.g., hydrogenation, P_(OH) being the compound obtained. P_(OH) being a free phenol.

In Step (c2) compounds (6), (8) or (11) are prepared from the P_(OH) derivatives (14), (16) or (17) by reaction with an appropriate alkylhalide in an inert solvent, in the presence of a base.

In Step (d), for the preparation of Compounds (7), (9) and (15), the protecting groups Pg may readily be removed by standard procedures preferably acid/base hydrolysis (e.g., formic acid at room temperature followed by extraction of the free base after treatment with sodium carbonate).

In Step (e), Compounds (7), (9) or (15) are subjected to a peptide coupling procedure with an appropriately protected acid of the formula R₁ CONHCH(P₂)CO₂ H or R₁ CO₂ H, using the herein-described procedures (or by any other coupling procedure currently available, or described in European Patent Application, Serial Number 93 401 785.6) to produce compounds (8) and (11) (from compound (7)); (10) and (12) (from compound (9)); and (16) and (17) (from compound (15)).

In Step (f), the oxidation may be effected via the well-known Swern oxidation procedure, or with 1,1,1-tris-(acetyloxy)-1,1-dihydro-1,2-benzodioxol-3(1H)-one. The latter is preferred when more than one basic group is present in the alcohol precursors (8) or (11). The oxidation procedures are effected according to standard procedures well known in the art.

In general the Swern oxidation see Synthesis, (1981), 165! is effected by reacting about 2 to 20 equivalents of dimethylsulfoxide (DMSO) with about 1 to 10 equivalents of trifluoromethylacetic anhydride (CF₃ CO)₂ O! or oxalyl chloride (COCl)₂ !, said reactants being dissolved in an inert solvent, e.g., methylene chloride (CH₂ Cl₂), said reaction being under an inert atmosphere (e.g., nitrogen or equivalently functioning gas) under anhydrous conditions at temperatures of about -70° C. to -30° C. to form an in situ sulfonium adduct to which is added about 1 equivalent of the appropriate alcohols, i.e., compounds (8) and (11). Preferably, the alcohols are dissolved in an inert solvent, e.g., CH₂ Cl₂, tetrahydrofuran, or minimum amounts of DMSO, and the reaction mixture is allowed to warm to about -50° C. or -20° C. (for about 20-60 minutes) and then the reaction is completed by adding about 3 to 30 equivalents of a tertiary amine, e.g., triethylamine, diisopropylethylamine, N-methyl morpholine, etc.

Another alternative process for converting the alcohols to the desired ketones is an oxidation reaction which employs periodane (i.e., 1,1,1-tris(acetyl)oxy-1,2-benzodioxol-3(1H)-one), see Dess Martin, J. Org. Chem., 48, 4155, (1983)!. This oxidation is effected by contacting about 1 equivalent of the alcohols with 1 to 5 equivalents of periodane (preferably 1.5 equivalents), said reagent being in suspension in an inert solvent (e.g., methylene chloride) under an inert atmosphere (preferably nitrogen) under anhydrous conditions at 0° C. to 50° C. (preferably room temperature) and allowing the reactants to interact for about 1 to 48 hours. Optional deprotection of the amine protecting groups may be effected as desired after the ketones have been isolated.

In general, the modified Jones oxidation procedure may conveniently be effected by reacting the alcohols with pyridinium dichromate by contacting the reactants together in a water-trapping molecular sieve powder, e.g., a grounded 3 Angstrom molecular sieve), wherein said contact is in the presence of glacial acetic acid at about 0° C. to 50° C., preferably at room temperature followed by isolation and then optionally removing amine protecting groups.

Alternatively, 1 to 5 equivalents of a chromic anhydride-pyridine complex (i.e., a Sarett reagent prepared in situ) see Fieser and Fieser "Reagents for Organic Synthesis" Vol. 1, pp. 145 and Sarett, et al., J.A.C.S. 25, 422, (1953)! said complex being prepared in situ in an inert solvent (e.g., CH₂ Cl₂) in an inert atmosphere under anhydrous conditions at 0° C. to 50° C. to which complex is added 1 equivalent of the alcohols allowing the reactants to interact for about 1 to 15 hours, followed by isolation and optionally removing amine protecting groups.

For the preparation of the necessary aldehydes of formula (3), and the preparation of the acids which are to be coupled with the amines of Formula (7), (9) or (15) alternative alkylation procedures are utilized depending upon whether the P₁ and/or the P₂ moieties are or are not residues of natural amino acids. The preparation of these intermediates wherein the P₁ or P₂ moieties are residues of natural amino acids (or minor modifications thereof, e.g., P₁ or P₂ being a benzyl or methyl ether of tyrosine), the compounds are either known or are prepared by processes and techniques well known in the art.

To prepare the intermediates of the formula ##STR17## wherein Pg is an amino protecting group, P₃ is either a P'₁ or P'₂ moiety with P'₁ and P'₂ being as defined for P₁ and P₂ respectively, except that they are other than residues of naturally occurring amino acids, and the R₉ moiety is an alkyl radical, preferably methyl when P₃ is P'₁, and ethyl when P₃ is P'₂, alternative methods are available.

To prepare the intermediates of formula ##STR18## the following reaction scheme may be utilized ##STR19## wherein P₃ is as previously defined and X is a leaving group, preferably halo or triflate, R₉ is methyl when P₃ is P'₁, and ethyl when P₃ is P'₂.

In essence, the preparation of compounds (19) utilizes the Krapcho method Tetrahedron Letters, 26, 2205 (1976)! for alkylation wherein compounds (18) are treated with a base, e.g., LDA, (lithium diisopropylamide), followed by reaction with the desired P₃ X in the presence of TMEDA (i.e. tetramethylethylenediamine) in a solvent (tetrahydrofuran) with or without HMPA (i.e. hexamethylphosphoramide) according to the standard Krapcho conditions. Following alkylation the compounds are then subjected to a reduction using diisobutylaluminium hydride (Dibal) in a mixture of solvents, e.g., ether, toluene, hexane, tetrahydrofuran at about -78° C. for about 1 hour. Following the preparation of the aldehydes of Formula (10B), the compounds are subjected to the processes of Reaction Schemes A, A' and/or A".

Alternatively, the compounds of (19) may be prepared by a Malonate/Curtius type sequence of reactions, see Yamada, et al., J. Amer. Chem. Soc., (1972) 94, 6203! as illustrated by the following reaction scheme ##STR20## wherein t-Bu is t-butyl, although other selectively removal acid protecting groups may be utilized, and P₃ X is as previously defined. This reaction involves the alkylation of the malonate ester (20) followed by selective removal of the t-butyl protecting group to produce compounds (22). These compounds are then transformed to (19) using the Curtius type rearrangement which entails their conversion to the protected amine via the intermediately formed azides, isocyanates, amines which are then protected with standard amino protecting groups, preferentially being protected in situ.

In the instance wherein P₃ represents a P'₁ moiety, the ester is transformed to the desired aldehydes of Formula (3) using standard Dibal reduction techniques, particularly in this situation (wherein P₁ is not a residue of a natural amino acid). Alternatively, (as is preferred when P₁ is a residue of a natural amino acid) the ester is de-esterified to its corresponding acid, converted to its corresponding hydroxamate and the hydroxamate upon treatment with lithium aluminum hydride is converted to its aldehyde. In the instance wherein P₃ represents a P'₂ moiety, the ethyl ester of compounds (19) are removed and the resulting compounds are ready for coupling as outlined in Reaction Scheme A'.

Having generically described the methods for the preparation of the compounds of this invention, the following specific examples illustrate the chemistry and techniques by which the synthesis may be effected.

The following examples present typical syntheses as described in Schemes A, A' or A". These examples are understood to be illustrative only and are not intended to limit the scope of the present invention in any way. As used herein, the following terms have the indicated meanings: "g" refers to grams; "mmol" refers to millimoles; "ml" refers to milliliters; "bp" refers to boiling point; "mp" refers to melting point; "°C." refers to degrees Celsius; "mm Hg" refers to millimeters of mercury; "μl" refers to microliters; "μg" refers to micrograms; and "μM" refers to micromolar; "Cbz" means carbobenzyloxy.

EXAMPLE 1 4-(N-BENZYLOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-OXO-5- 4(2-{N-MORPHOLINYL}ETHYLOXY)PHENYL!N-BENZYL PENTANAMIDE ##STR21## STEP A 4-TERT-BUTOXYCARBONYLAMINO-2,2-DIFLUORO-3-HYDROXY-5 (4-BENZYLOXY)PHENYL!N-BENZYL PENTANAMIDE

To a solution of 4-tert-butoxycarbonylamino-2,2-difluoro-3-hydroxy-5- (4-benzyloxy)phenyl!pentanoic acid, ethyl ester, compound described in Patent Application PCT/US91/09741, filed 20 Dec. 1991 incorporated herein by reference, (4.79 g, 10 mmol) in anhydrous tetrahydrofuran (25 ml) was added benzylamine (6.42 g, 60 mmol). The mixture was stirred at room temperature overnight. The crude mixture was diluted with ethyl acetate (150 ml), washed with 0.1N aqueous hydrochloric acid (3×50 ml), water (50 ml) and brine (50 ml). The organic layer was dried over anhydrous magnesium sulphate.

After filtration and removal of the solvent in vacuo the residue was purified by flash chromatography (silica gel, ethyl acetate/cyclohexane: 2:8) to give the title compound (3.80 g, 71% yield).

Rf: 0.47 (ethyl acetate/cyclohexane)

mp: 142° C.

MS: MH!⁺ =541 MNH₄ !⁺ =558

Analysis: for C₃₀ H₃₄ N₂ O₅ F₂, Calculated: C, 66.65; H, 6.34; N, 5.18 Found: C, 66.96; H, 6.34; N, 5.15.

STEP B

4-AMINO-2,2-DIFLUORO-3-HYDROXY-5 (4-BENZYLOXY)PHENYL!N-BENZYL PENTANAMIDE

A solution of 4-tert-butoxycarbonylamino-2,2-difluoro-3-hydroxy-5 (4-benzyloxy)phenyl!N-benzyl pentanamide (0.65 g, 1.2 mmol) in formic acid (20 ml) was stirred at room temperature for 4 hours. The solvent was removed in vacuo. The residue was dissolved in ethyl acetate (60 ml) and washed with a saturated solution of sodium carbonate (3×10 ml), and brine (10 ml). The organic layer was dried over magnesium sulphate.

Filtration and removal of the solvent in vacuo yielded the title compound as a white solid (0.42 g, 80% yield) used without further purification in the next step.

Rf: 0.62 (AcOH/nBuOH/H₂ O: 2:6:2

MS: MH!⁺ =441

Analysis: for C₂₅ H₂₆ N₂ O₃ F₂, Calculated: C, 68.17; H, 5.95; N, 6.36 Found: C, 67.88; H, 5.88; N, 6.56.

STEP C

4(N-TERT-BUTOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-5 (4-BENZYLOXY)PHENYL!N-BENZYL PENTANAMIDE

To a solution of N-tert-butoxycarbonyl-L-valyl-anhydride (0.387 g, 0.93 mmol) in anhydrous dichloromethane (10 ml) at room temperature, was added a solution of 4-amino-2,2-difluoro-3-hydroxy-5 (4-benzyloxy)phenyl!N-benzyl pentanamide (0.41 g, 0.93 mmol) in anhydrous N,N-dimethylformamide (3 ml) and anhydrous dichloromethane (2 ml). The mixture was stirred at room temperature overnight.

Evaporation and purification of the residue by flash chromatography (silica gel, gradient of ethyl acetate/cyclohexane: 2:8 to 1:1) afforded a white solid (0.45 g, 76% yield).

Rf: 0.38 (AcOEt/cyclohexane: 1:1)

MS: MH!⁺ =640

Analysis: for C₃₅ H₄₃ N₃ O₆ F₂, Calculated: C, 65.71; H, 6.77; N, 6.57 Found: C, 65.92; H, 6.87; N, 6.45.

STEP D

4(N-TERT-BUTOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-5 (4-(HYDROXY)PHENYL!N-BENZYL PENTANAMIDE

To a solution of 4(N-tert-butoxycarbonyl-L-valyl)amino-2,2-difluoro-3-hydroxy-5 (4-benzyloxy)phenyl!N-benzyl pentanamide (0.35 g, 0.55 mmol) in absolute ethanol (15 ml) and anhydrous N,N-dimethylformamide (5 ml) was added 10% Palladium in activated charcoal (0.1 g). This mixture was stirred at room temperature under atmospheric pressure of hydrogen overnight.

Filtration of the catalyst and evaporation in vacuo yielded 90% of the title compound (0.27 g) as a white solid.

Rf: 0.29 (ethyl acetate/cyclohexane: 1:1).

STEP E

4(N-TERT-BUTOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-5 4(2-{N-MORPHOLINYL}ETHYLOXY)PHENYL!N-BENZYL PENTANAMIDE

To a solution of 4(N-tert-butoxycarbonyl-L-valyl)amino-2,2-difluoro-3-hydroxyl-5 4(hydroxy)phenyl!N-benzyl pentanamide (0.27 g, 0.49 mmol) in anhydrous dioxane (20 ml) was added anhydrous cesium carbonate (0.422 g, 1.3 mmol), potassium iodide (0.01 g) and N-(2-chloroethyl) morpholine hydrochloride (0.111 g, 0.6 mmol). This mixture was heated under reflux for 72 hours. The crude mixture was diluted with ethyl acetate (100 ml) and washed three times with water and brine. The organic layer was dried over magnesium sulphate.

Filtration and evaporation of the solvent in vacuo afforded a residue which was purified by flash chromatography (silica gel, ethyl acetate). The title compound was obtained with 62% yield (0.2 g).

Rf: 0.33 (CHCl₃ /CH₃ H: 92:8)

MS: MH!⁺ =663.

STEP F

4(L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-5 4(2-{N-MORPHOLINYL}ETHYLOXY)PHENYL!N-BENZYL PENTANAMIDE

A solution of 4(N-tert-butoxycarbonyl-L-valyl)amino-2,2-difluoro-3-hydroxy-5 4(2-{N-MORPHOLINYL}ETHYLOXY)PHENYL!N-benzyl pentanamide (0.19 g, 0.28 mmol) in formic acid (15 ml) was stirred at room temperature for 4 hours. After evaporation of the solvent in vacuo, the residue was diluted with ethyl acetate (50 ml) and washed three times with a saturated solution of sodium carbonate (3×10 ml) and brine (10 ml). The organic layer was dried over magnesium sulphate.

Filtration and removal of the solvent in vacuo yielded the title compound as a white solid used without purification in the next step (0.11 g, 69% yield).

STEP G

4(N-BENZYLOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-5 4(2-{N-MORPHOLINYL}ETHYLOXY)PHENYL!N-BENZYL PENTANAMIDE

To a solution of 4(L-valyl)amino-2,2-difluoro-3-hydroxy-5 4(2-{N-MORPHOLINYL}ETHYLOXY)PHENYL!N-benzyl pentanamide (0.1 g, 0.18 mmol) in anhydrous dichloromethane (10 ml) was added benzyldicarbonate (0.055 g, 0.19 mmol). The mixture was stirred at room temperature overnight.

Evaporation of the solvent in vacuo, purification of the residue by flash chromatography (silica gel, CH₂ Cl₂ /CH₃ OH: 99:1) and recrystallization (ethyl acetate/pentane) afforded the title compound as a white solid (0.075 g, 60% yield).

Rf: 0.38 (chloroform/methanol: 92:8)

MS: MH!⁺ =697

Analysis: for C₃₇ H₄₆ N₄ O₇ F₂, Calculated with 0.25 H₂ O: C, 63.77; H, 6.68; N, 7.98 Found: C, 63.34; H, 6.64; N, 8.08.

STEP H

4(N-BENZYLOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-OXO-5- 4(2-{N-MORPHOLINYL}ETHYLOXY)PHENYL!N-BENZYL PENTANAMIDE

To a solution of oxalyl chloride (0.102 g, 0.8 mmol) in anhydrous dichloromethane (1 ml) at -60° C., was added under nitrogen, dimethyl sulfoxide (distilled over calcium hydride) (0.125 g, 1.6 mmol) in anhydrous dichloromethane (1 ml). After 10 minutes stirring a solution of 4(N-benzyl-oxycarbonyl-L-valyl)amino-2,2-difluoro-3-hydroxy-5 4(2-{N-MORPHOLINYL}ETHYLOXY)PHENYL!N-benzyl pentanamide (0.06 g, 0.08 mmol) in anhydrous dichloromethane (3 ml) was added. The mixture was stirred at -60° C. for 3 hours and the temperature was then allowed to rise to -10° C. Triethylamine (0.101 g, 1 mmol) in anhydrous dichloromethane (1 ml) was then added. The mixture was stirred for 15 hours while the temperature was allowed to rise to room temperature. The crude mixture was taken off in ethyl acetate (30 ml) and washed with 0.1N aqueous hydrochloric acid (3×8 ml), brine (8 ml) and dried over magnesium sulphate.

Filtration and removal of the solvent in vacuo yielded a crude residue which was purified by flash chromatography (silica gel, chloroform/methanol: 99:1). The title compound was isolated as a white solid (0.036 g, 61% yield).

Rf: 0.40 (chloroform/methanol: 92:8)

MS: MH!⁺ =695

Analysis: for C₃₇ H₄₄ N₄ O₇ F₂, Calculated: C, 63.96; H, 6.38; N, 8.06 Found: C, 64.10; H, 6.50; N, 7.65

¹⁹ F NMR: shows mixture of two stereoisomers (40/60) and ketone/hydrate: 75/25.

EXAMPLE 2 4-(N-BENZYLOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-OXO-5 4({2-pyridyl}methyloxy)phenyl!N-BENZYL PENTANAMIDE ##STR22## STEP A 4-TERT-BUTOXYCARBONYLAMINO-2,2-DIFLUORO-3-HYDROXY-5 (4-HYDROXY)PHENYL!N-BENZYL PENTANAMIDE

A solution of 4-(tert-butoxycarbonylamino-2,2-difluoro-3-hydroxy-5- (4-benzyloxy)phenyl!N-benzyl-pentanamide (1.90 g, 3.5 mmol) in absolute ethanol (100 ml) was stirred with 10% Palladium on charcoal (0.6 g) at room temperature under atmospheric pressure of hydrogen overnight.

Filtration of the catalyst and evaporation in vacuo of the filtrate, yielded 89% of the title compound (1.40 g) as a white solid.

Rf: 0.38 (ethyl acetate/cyclohexane)

Analysis: for C₂₃ H₂₈ N₂ O₅ F₂, 0.25 H₂ O: Calculated: C, 60.72; H, 6.31; N, 6.16 Found: C, 60.60; H, 6.25; N, 6.03.

STEP B

4-TERT-BUTOXYCARBONYLAMINO-2,2-DIFLUORO-3-HYDROXY-5 4({2-pyridyl}methyloxy)phenyl!N-BENZYL PENTANAMIDE

To a solution of 4-tert-butoxycarbonylamino-2,2-difluoro-3-hydroxy-5 (4-hydroxy)phenyl!N-benzyl pentanamide (0.59 g, 1.3 mmol) in anhydrous dioxane (25 ml) was added anhydrous cesium carbonate (1.11 g, 3.4 mmol), potassium iodide (0.01 g) and 2-picolylchloride hydrochloride (0.246 g, 1.5 mmol). This mixture was heated under reflux for 6 hours. The crude mixture was diluted with ethyl acetate (150 ml) and washed three times with water and once with brine. The organic layer was dried over magnesium sulphate.

Filtration and evaporation in vacuo of the solvent afforded a residue which was purified by flash chromatography (silica gel, gradient of ethylacetate/cyclohexane: 3:7 to 1:1). The title compound was isolated with 40% yield (0.23 g).

Rf: 0.49 (AcOEt/cyclohexane: 1:1)

MS: MH!⁺ =542.

STEP C

4-AMINO-2,2-DIFLUORO-3-HYDROXY-5 4({2-pyridyl)methyloxy)phenyl!N-BENZYL PENTANAMIDE

A solution of 4-tert-butoxycarbonylamino-2,2-difluoro-3-hydroxy-5 4({2-pyridyl}methyloxy)phenyl!N-benzyl pentanamide (0.28 g, 0.52 mmol) in formic acid (25 ml) was stirred at room temperature for 4 hours. The solvent was removed in vacuo. The residue was dissolved with ethyl acetate (60 ml) and washed with a saturated solution of sodium carbonate (3×20 ml) and brine, then dried over magnesium sulphate.

Filtration and removal of the solvent in vacuo yielded the title compound as a white solid (0.17 g, 75% yield) used without purification in the next step.

STEP D

4-(N-BENZYLOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-5 4({2-pyridyl}methyloxy)phenyl!N-BENZYL PENTANAMIDE

To a solution of Cbz-L-valyl-anhydride (0.184 g, 0.38 mmol) in anhydrous dichloromethane (8 ml) was added 4-amino-2,2-difluoro-3-hydroxy-5 4({2-pyridyl}methyloxy)phenyl!N-benzyl pentanamide (0.17 g, 0.38 mmol) in anhydrous dichloromethane (3 ml) and anhydrous N-N dimethylformamide (1 ml). This mixture was stirred at room temperature overnight.

The solvent was removed in vacuo and the residue purified by flash chromatography (silica gel, gradient of ethyl acetate/cyclohexane: 3:7 to 75:25). The title compound was isolated as a white solid (0.195 g, 76% yield).

Rf: 0.45 (ethyl acetate)

MS: MH!⁺ =675

Analysis: for C₃₇ H₄₀ N₄ O₆ F₂, Calculated: C, 64.15; H, 6.11; N, 8.09 Found: C, 64.31; H, 6.05; N, 7.96

¹⁹ F NMR: shows mixture of 2 diastereoisomers 85/15.

STEP E

4-(N-BENZYLOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-OXO-5 4({2-pyridyl}methyloxy)phenyl!N-BENZYL PENTANAMIDE

To a solution of oxalyl chloride (0.303 g, 2.5 mmol) in anhydrous dichloromethane (3 ml) at -60° C. under nitrogen, was added a solution of dimethylsulfoxide (0.39 g, 5 mmol) in anhydrous dichloromethane (1 ml). After stirring for 10 minutes, a solution of 4-(N-benzyloxycarbonyl-L-valyl)-amino-2,2-difluoro-3-hydroxy-5 4({2-pyridyl}methyloxy)phenyl!N-benzyl pentanamide (0.17 g, 0.25 mmol) in anhydrous dichloromethane (4 ml) was added. The mixture was stirred at -60° C. under nitrogen for 3 hours and the temperature was then allowed to rise to -10° C. Triethylamine (0.303 g, 3 mmol) in anhydrous dichloromethane (1 ml) was then added. The mixture was stirred for 15 hours while the temperature was allowed to rise to room temperature. The crude mixture was taken off in ethyl acetate (50 ml) and washed with 0.1N aqueous hydrochloric acid (3×10 ml). The organic layer was washed with water, brine and dried over magnesium sulphate.

After filtration and removal of the solvent in vacuo the residue was purified by flash chromatography (silica gel, gradient of ethyl acetate/cyclohexane: 4:6 to 75:25). The title compound was isolated as a white solid (0.09 g, 53% yield).

Rf: 0.50 (AcOEt)

MS: ME!⁺ =673

Analysis: for C₃₇ H₃₈ N₄ O₆ F₂, Calculated: C, 66.06; H, 5.69; N, 8.33 Found: C, 66.12; H, 5.77; N, 8.15

¹⁹ F NMR: shows mixture of 2 stereoisomers 40/60.

EXAMPLE 3 4-(N-BENZYLOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-OXO-5- 4-(OXO-4-PENTENYL)PHENYL!N-BENZYL PENTANAMIDE ##STR23## STEP A 4-TERT-BUTOXYCARBONYLAMINO-2,2-DIFLUORO-3-HYDROXY-5 4-(OXO-4-PENTENYL)PHENYL!N-BENZYL PENTANAMIDE

To a solution of the compound described in Example 2, Step A (0.45 g, 1 mmol) in anhydrous dioxane (15 ml) was added anhydrous potassium carbonate (0.116 g, 1.2 mmol), potassium iodide (0.01 g) and 5-bromo-1-pentene (1.64 g, 11 mmol). The mixture was heated under reflux for 3 days.

The crude mixture was diluted with ethyl acetate (100 ml) and washed three times with water and once with brine. The organic layer was dried over magnesium sulphate.

Filtration and evaporation in vacuo of the solvent afforded a residue, which was purified by flash chromatography (silica gel, gradient of ethyl acetate/cyclohexane 1:9 to 2:8). The title compound was isolated as a white solid with 31% yield (0.16 g).

Rf: 0.53 (AcOEt/cyclohexane: 1:1)

MS: MH!⁺ =519 MNH₄ !⁺ =536.

STEP B

4-AMINO-2,2-DIFLUORO-3-HYDROXY-5 4-(OXO-4-PENTENYL)PHENYL!N-BENZYL PENTANAMIDE

A solution of 4-tert-butoxycarbonylamino-2,2-difluoro-3-hydroxy-5 4-(oxo-4-pentenyl)phenyl!N-benzyl pentanamide (0.16 g, 0.30 mmol) in formic acid (10 ml) was stirred at room temperature for 4 hours. The solvent was removed in vacuo.

The residue was dissolved in ethyl acetate (60 ml) and washed three times with a saturated solution of sodium carbonate (3×20 ml) and brine (20 ml), then dried over anhydrous magnesium sulphate.

Filtration and removal of the solvent in vacuo yielded the title compound as a white solid (0.08 g, 63% yield) used without purification in the next step.

STEP C

4-(N-BENZYLOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-5- 4-(OXO-4-PENTENYL)PHENYL!N-BENZYL PENTANAMIDE

To a solution of Cbz-L-Valyl anhydride (0.092 g, 0.20 mmol) in anhydrous dichloromethane (10 ml) was added 4-amino-2,2-difluoro-3-hydroxy-5 4-(oxo-4-pentenyl)phenyl!N-benzyl pentanamide (0.08 g, 0.19 mmol) in anhydrous dichloromethane (3 ml). The mixture was stirred at room temperature overnight.

The solvent was removed in vacuo and the residue purified by flash chromatography (silica gel, ethyl acetate/cyclohexane: 3:7).

The title compound was isolated as a white solid (0.09 g, 73% yield).

Rf: 0.37 (ethyl acetate/cyclohexane: 1:1)

MS: MH!⁺ =652.

STEP D

4-(N-BENZYLOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-OXO-5 4-(OXO-4-PENTENYL)PHENYL!N-BENZYL PENTANAMIDE

To a solution of oxalyl chloride (0.178 g, 1.4 mmol) in anhydrous dichloromethane (10 ml) at -60° C. under nitrogen was added a solution of anhydrous dimethyl sulfoxide (0.218 g, 2.8 mmol) in anhydrous dichloromethane (1 ml). After 10 minutes stirring a solution of 4-(N-benzyloxycarbonyl-L-valyl)amino-2,2-difluoro-3-hydroxy-5 4-oxo-4-pentenyl)phenyl!N-benzyl pentanamide (0.09 g, 0.14 mmol) in anhydrous dichloromethane (3 ml) was added.

The mixture was stirred at -60° C. under nitrogen for 3 hours and the temperature was then allowed to rise to -10° C. Triethylamine (0.162 g, 1.6 mmol) in anhydrous dichloromethane (1 ml) was then added. The mixture was stirred for 15 hours while the temperature was allowed to rise to room temperature.

The crude mixture was taken off in ethylacetate (50 ml) and washed with 0.1N aqueous hydrochloric acid (3×10 ml). The organic layer was washed with water, brine and dried over anhydrous magnesium sulphate.

After filtration and removal of the solvent in vacuo, the residue was purified by flash chromatography (silica gel, ethyl acetate/cyclohexane 2:8).

The title compound was obtained as a white solid (0.038 g, 43% yield).

Rf: 0.39 (ethyl acetate/cyclohexane: 1:1)

MS: MH!⁺ =650 MNH₄ !⁺ =667

Analysis: for C₃₆ H₄₁ N₃ _(O) ₆ F₂, Calculated: C, 66.55; H, 6.36; N, 6.47 Found: C, 65.75; H, 6.09; N, 5.79

¹⁹ F NMR: shows mixture of 2 stereoisomers 65/35 and ketone/hydrate 83/17.

EXAMPLE 4 N 3-(3-PYRIDYL)PROPANOYL!4-(L-VALYL)AMINO-2,2-DIFLUORO-3-OXO-5 4-2{N-morpholinyl}ethyloxy)phenyl!N-BENZYL PENTANAMIDE ##STR24## STEP A N 3-(3-PYRIDYL)PROPANOYL!4-(L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-5 4(2-{N-MORPHOLINYL}ETHYLOXY)PHENYL!N-BENZYL PENTANAMIDE

To a solution of N- 3-(3-pyridyl)propanoyl!4-(L-valyl)amino-2,2-difluoro-3-hydroxy-5 (4-hydroxy)phenyl!N-benzyl pentanamide (0.17 g, 0.29 mmol) in anhydrous dioxane (20 ml) was added anhydrous cesium carbonate (0.325 g), 1 mmol) potassium iodide (0.01 g) and N-2-chloroethyl morpholine hydrochloride (0.075 g, 0.40 mmol). This mixture was heated under reflux overnight. The crude mixture was evaporated in vacuo and the residue was purified by flash chromatography (silica gel, gradient of dichloromethane:methyl alcohol: 98:2 to 92:8).

The title compound was isolated as a white solid (75% yield, (0.15 g).

Rf: 0.49 (dichloromethane/methyl alcohol: 9:1)

MS: MH!⁺ =696

STEP B

N 3-(3-PYRIDYL)PROPANOYL!4-(L-VALYL)AMINO-2,2-DIFLUORO-3-OXO-5 4(2-{N-MORPHOLINYL}ETHYLOXY)PHENYL!N-BENZYL PENTANAMIDE

To a solution of oxalyl chloride (0.254 g, 2 mmol) in anhydrous dichloromethane under nitrogen at -60° C., was added a solution of dimethyl sulfoxide (0.312 g, 4 mmol) in anhydrous dichloromethane (2 ml). After 10 minutes stirring at -60° C., a solution of N 3-(3-pyridyl)propanoyl!4-(L-valyl)amino-2,2-difluoro-3-hydroxy-5 4(2-{N-morpholyl}ethyloxy)phenyl!N-benzyl pentanamide (0.14 g, 0.20 mmol) in anhydrous dichloromethane (5 ml) was added.

The mixture was stirred at -60° C. under nitrogen for 4 hours and then the temperature was allowed to rise to -10° C. Triethylamine (0.303 g, 3 mmol) in anhydrous dichloromethane (1 ml) was then added and the mixture was stirred under nitrogen for 15 hours, while the temperature was allowed to rise to room temperature. The crude mixture was taken off in ethylacetate (50 ml) and washed with water (3×10 ml) and brine (10 ml) then dried over anhydrous magnesium sulphate.

Filtration and removal of the solvent in vacuo afforded a residue which was purified by flash chromatography (silica gel, gradient of dichloromethane/methanol: 98:2 to 92:8). The title compound was isolated as a pale yellow solid (10% yield, 0.014 g).

Rf: 0.51 (dichloromethane/methanol: 9:1)

MS: MH!⁺ =694

EXAMPLE 5 N 3-(3-PYRIDYL)PROPANOYL!4-(L-VALYL)AMINO-2,2-DIFLUORO-3-OXO-5 4({2-pyridyl}methyloxy)phenyl!N-BENZYL PENTANAMIDE ##STR25## STEP A 4-(L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-5 (4-(BENZYLOXY) PHENYL!N-BENZYL PENTANAMIDE

A solution of 4(N-tert-butoxycarbonyl-L-valyl)amino-3,3-difluoro-3-hydroxy-5 (4-benzyloxy)phenyl!N-benzyl pentanamide (1.28 g, 2 mmol) in formic acid (50 ml) was stirred at room temperature for 4 hours. The solvent was removed in vacuo and the residue was dissolved in ethyl acetate (100 ml) and washed three times with a saturated solution of sodium carbonate (3×30 ml), once with brine (30 ml). The organic layer was dried over anhydrous magnesium sulphate.

Filtration and removal of the solvent in vacuo yielded the title compound as a white solid (0.90 g, 84% yield), used without purification in the next step.

STEP B

N 3-(3-PYRIDYL)PROPANOYL!4-(L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-5 (4-BENZYLOXY)PHENYL!N-BENZYL PENTANAMIDE

To a solution of 3-(3-pyridyl)propionic acid (0.242 g, 1.6 mmol) in anhydrous acetonitrile (10 ml) was added N-methyl morpholine (0.182 g, 1.8 mmol) in anhydrous acetonitrile (1 ml). The mixture under nitrogen was cooled to -20° C. and isobutylchloroformate (0.218 g, 1.6 mmol) in anhydrous acetonitrile (2 ml) was added. After 10 minutes stirring at -20° C. under nitrogen, 4-(L-valyl)amino-2,2-difluoro-3-hydroxy-5 (4-benzyloxy)phenyl!N-benzyl pentanamide (0.9 g, 1.6 mmol) in anhydrous N,N-dimethyl formamide (10 ml) was added.

The mixture was stirred at -20° C. under nitrogen for 4 hours and then the temperature was allowed to rise to room temperature overnight. The crude mixture was evaporated in vacuo and the residue was purified by flash chromatography (silica gel, gradient of dichloromethane/methyl alcohol: 99:1 to 92:8). The title compound was obtained as a white solid (0.8 g, 75% yield).

Rf: 0.36 (dichloromethane/methanol: 92:8)

MS: MH!⁺ =673

Analysis: for C₃₆ H₄₂ N₄ O₅ F₂, Calculated: C, 66.95; H, 6.36; N, 8.22 Found: C, 66.71; H, 6.19; N, 8.04

STEP C

N 3-(3-PYRIDYL)PROPANOYL4-(L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-5 (4-HYDROXY)PHENYL!N-BENZYL PENTANAMIDE

A solution of N 3-(3-pyridyl)propanoyl!4-(L-valyl)-amino-2,2-difluoro-3-hydroxy-5 (4-benzyloxy)phenyl!N-benzyl pentanamide (0.43 g, 0.64 mmol) in absolute ethanol (20 ml) and N,N-dimethylformamide (5 ml) was stirred with 10% palladium on charcoal (0.12 g) at room temperature under atmospheric pressure of hydrogen overnight.

Filtration of the catalyst and evaporation in vacuo of the filtrate, yielded 81% the title compound (0.3 g) as a white solid.

Rf: 0.20 (dichloromethane/methanol: 92:8)

MS: MH!⁺ =582

STEP D

N 3-(3-PYRIDYL)PROPANOYL!4-(L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-5 4({2-pyridyl}methyloxy)phenyl!N-BENZYL PENTANAMIDE

To a solution of N 3-(3-pyridyl)propanoyl!4-(L-valyl)amino-2,2-difluoro-3-hydroxy-5 (4-(hydroxy)phenyl!N-benzyl pentanamide (0.3 g, 0.51 mmol) in anhydrous dioxane (50 ml) was added anhydrous cesium carbonate (0.43 g, 1.3 mmol) potassium iodide (10 mg) and 2-picolyl chloride (0.108 g, 0.66 mmol). This mixture was heated under reflux for 30 hours. The crude mixture was diluted with ethyl acetate (100 ml) and washed three times with water (3×20 ml) and once with brine. The organic layer was dried over anhydrous magnesium sulphate.

Filtration and evaporation in vacuo of the solvent afforded a residue which was purified by flash chromatography (silica gel, gradient of dichloromethane/methyl alcohol: 98:2 to 92:8). The title compound was isolated as a white solid (41% yield, 0.140 g).

Rf: 0.47 (dichloromethane/methanol: 9:1)

MS: MH!⁺ =674

Analysis: for C₃₇ H₄₁ N₅ O₅ F₂, Calculated: C, 65.96; H, 6.13; N, 10.39 Found: C, 64.13; H, 5.87; N, 10.11

¹⁹ F NMR: shows mixture of stereoisomers 80/20.

STEP E

N 3-(3-PYRIDYL)PROPANOYL!4-(L-VALYL)AMINO-2,2-DIFLUORO-3-OXO-5 4({2-pyridyl}methyloxy)phenyl!N-BENZYL PENTANAMIDE

To a solution of oxalyl chloride (0.085 g, 0.67 ml) in anhydrous dichloromethane (5 ml) under nitrogen at -60° C., was added a solution of dimethylsulfoxide (0.11 g, 0.70 mmol) in anhydrous dichloromethane (2 ml). After 10 minutes stirring at -60° C., a solution of N(3-(3-pyridyl)propanoyl!4-(L-valyl)amino-2,2-difluoro-3-hydroxy-5 4({2-pyridyl}methyloxy)phenyl!N-benzyl pentanamide (0.045 g, 0.067 mmol) in anhydrous dichloromethane (3 ml) was added. The mixture was stirred at -60° C. under nitrogen for 4 hours and then the temperature was allowed to rise to -10° C. Triethylamine (0.202 g, 2 mmol) in anhydrous dichloromethane (2 ml) was then added, and the mixture was stirred for 15 hours, while the temperature was allowed to rise to room temperature. The crude mixture was taken off in ethyl acetate (50 ml) and washed with 0.1N aqueous hydrochloric acid (3×10 ml). The organic layer was washed with water brine and dried over magnesium sulphate.

After filtration and removal of the solvent in vacuo the residue was purified by flash chromatography (silica gel, gradient of dichloromethane/methyl alcohol): 98:2 to 95:5). The title compound was isolated as a white solid 44% yield, 0.019 g).

Rf: 0.50 (dichloromethane/methanol: 9:1)

MS: MH!⁺ =672

EXAMPLE 6 N- 4-(N-Benzyloxycarbonyl-L-valyl)amino-2,2-difluoro-1,3-dioxo-5-(4-{2-N-morpholinyl}ethyloxy)phenyl-pentyl!-O-benzyl-D-valinol ##STR26## STEP A 4-TERT-BUTOXYCARBONYLAMINO-2,2-DIFLUORO-3-HYDROXY-5-(4-HYDROXY)PHENYL PENTANOIC ACID, ETHYL ESTER

A solution of 4-tert-butoxycarbonylamino-2,2-difluoro-3-hydroxy-5- (4-benzyloxy)phenyl!N-benzyl pentanamide (0.719 g, 1.5 mmol) in ethanol (50 ml) was kept for 7.5 hours under an hydrogen atmosphere in the presence of 10% palladium on charcoal (0.074 g). The hydrogen atmosphere was exchanged by a nitrogen atmosphere, the suspension was filtered off and the solution concentrated in vacuo. The title derivative thus obtained was used as such in the next step (0.500 g, 83% yield).

Rf: 0.51 (silica gel, petroleum ether/ethyl acetate: 1/1).

STEP B

N-TERT-BUTOXYCARBONYL-D-VALINOL

A solution of D-valinol (5.1 g, 49.4 mmol) and di-tert-butyldicarbonate (10.9 g, 52 mmol) in methanol (60 ml) was stirred for 17 hours at room temperature. After concentration in vacuo, the residue was purified by flash chromatography (silica gel, ethyl acetate/petroleum ether: 3/7, Rf: 0.37) to give the title compound in quantitative yield (10.07 g, colorless oil).

MS: MH⁺ =204.

STEP C

N-TERT-BUTOXYCARBONYL-O-BENZYL-D-VALINOL

To a solution of N-tert-butoxycarbonyl-D-valinol (10 g, 49.3 mmol) and benzylbromide (5.86 ml, 49.3 mmol) in anhydrous dimethyl formamide (50 ml) was added at -5° C. and under nitrogen, potassium-tert-butoxide (11.06 g, 98.6 mmol) as a solid, portionwise, an in such a way that the internal temperature does not exceed +5° C. The reaction mixture was stirred for 2 hours at 0° C., diluted with ethyl acetate (2×300 ml), extracted with a 1N solution of potassium hydrogenosulfate (50 ml) and water (250 ml) and washed twice with water (2×200 ml). After drying of the organic phase on sodium sulfate, filtration and concentration in vacuo, the resulting oil was purified by flash chromatography (silica gel, ethyl acetate/petroleum ether: 1/9, Rf: 0.42) to give the title compound as a colorless oil (9.95 g, 69% yield).

MS: MH!⁺ =294.

STEP D

O-BENZYL-D-VALINOL

A solution of N-tert-butoxycarbonyl-O-benzyl-D-valinol (9.95 g, 34 mmol) in formic acid (50 ml) was stirred for 4 hours at room temperature. After removal of the formic acid in vacuo, the sticky residue was dissolved in water (100 ml), neutralized with a saturated solution of sodium bicarbonate (100 ml) and the organic material extracted twice with ethyl acetate (2×200 ml). The organic phases were washed until neutral with water (2×200 ml) and the combined organic layers were dried on sodium sulfate. Filtration and evaporation of the solvent in vacuo afforded the title amine as a slightly yellowish oil (5.20 g, 79%).

MS: MH!⁺ =194.

STEP E

N- 4-TERT-BUTOXYCARBONYLAMINO-2,2-DIFLUORO-3-HYDROXY-1-OXO-5-(4-HYDROXY)PHENYL-PENTYL!O-BENZYL-D-VALINOL

The title compound is obtained from the compounds described in Example 6, Steps A and D, following the method given in Example 1, Step A.

STEP F

N- 4-TERT-BUTOXYCARBONYLAMINO-2,2-DIFLUORO-3-HYDROXY-1-OXO-5-(4-(2-N-MORPHOLINYL)ETHYLOXY)PHENYL-PENTYL!O-BENZYL-D-VALINOL

The title derivative is obtained from the phenol of Example 6, Step E and N-(2-chloroethyl)morpholine, hydrochloride using the procedure of Example 1, Step E.

STEP G

N- 4-AMINO-2,2-DIFLUORO-3-HYDROXY-1-OXO-5-(4-{2-N-MORPHOLINYL}ETHYLOXY)PHENYL-PENTYL!O-BENZYL-D-VALINOL

The title amine is prepared from the compound of Example 6, Step F using the deprotection procedure described in Example 1, Step B.

STEP H

N- 4-(N-BUTOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-1OXO-5-(4-{2-N-MORPHOLINYL}ETHYLOXY)PHENYL-PENTYL!O-BENZYL-D-VALINOL

The title compound is obtained from the amine of Example 6, Step G and N-benzyloxycarbonyl-L-valyl anhydride following the procedure given in Example 1, Step C.

STEP I

N- 4-(N-BENZYLOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-1,3-DIOXO-5-(4-{2-N-MORPHOLINYL}ETHYLOXY)PHENYL-PENTYL!O-BENZYL VALINOL

The title derivative is obtained from the alcohol of Example 6, Step H using the oxidation method described in Example 1, Step H.

EXAMPLE 7 N- 4-(N-BENZYLOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-1,3-DIOXO-5-(4-{2-N-MORPHOLINYL}ETHYLOXY)PHENYL-PENTYL!O-METHYL-D-VALINOL ##STR27## STEP A N-TERT-BUTOXYCARBONYL-O-METHYL-D-VALINOL

The title compound has been prepared in 67% yield from the alcohol of Example 6, Step B and methyl iodide following the alkylation method given in Example 6, Step C.

Rf: 0.27 (silica gel, ethyl acetate/petroleum ether: 1/9).

STEP B

O-METHYL-D-VALINOL

A solution of compound of Example 7, Step A (1.9 g, 8.76 mmol) in dry diethyl ether saturated with HCl gas was kept for 2 hours at room temperature. The solvent was removed in vacuo. The residue was dissolved in a minimum amount of a 95/5 mixture of dichloromethane and diethylamine and purified by flash chromatography on silica gel using the same mixture of solvents. The title amine was obtained in 59% yield.

Rf: 0.01 (ethyl acetate/methanol: 8/2).

STEP C

N- 4-TERT-BUTOXYCARBONYLAMINO-2,2-DIFLUORO-3-HYDROXY-1OXO-5-(4-HYDROXY)PHENYL-PENTYL!O-METHYL-D-VALINOL

The title derivative is obtained from the compound of Example 6, Step A and the amine of Example 7, Step B following the reaction procedure given in Example 1, Step A (79% yield).Rf: 0.16 (ethylacetate/petroleum ether: 4:6)

MS: MH!⁺ =461.

STEP D

N- 4-TERT-BUTOXYCARBONYLAMINO-2,2-DIFLUORO-3-HYDROXY-1OXO-5-(4-{2-N-MORPHOLINYL}ETHYLOXY)PHENYL-PENTYL!O-METHYL-D-VALINOL

The title compound is prepared from the phenol of Example 7, Step C and N-(2-chloroethyl)morpholine, hydrochloride using the method described in Example 1, Step E (58% yield).

Rf: 0.18 (ethylacetate).

STEP E

N- 4-AMINO-2,2-DIFLUORO-3-HYDROXY-1OXO-5-(4-{(2-N-MORPHOLINYL}ETHYLOXY)PHENYL-PENTYL!O-METHYL-D-VALINOL

The title amine is obtained from the compound of Example 7, Step D using the deprotection method given in Example 1, Step B (85% yield).

STEP F

N- 4(N-BENZYLOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-3-HYDROXY-1-OXO-5-(4-{2-N-MORPHOLINYL}ETHYLOXY)PHENYL-PENTYL!O-METHYL-D-VALINOL

The title alcohol is obtained from the amine of Example 7, Step E and N-benzyloxycarbonyl-L-valyl anhydride using the coupling procedure given in Example 1, Step C (78% yield).

Rf: 0.24 (dichloromethane/methanol: 95:5)

MS: M!⁺ =707

Analysis: for C₃₆ H₅₂ N₄ O₈ F₂, 0.5 H₂ O Calculated: C, 60.40; H, 7.46; N, 7.83 Found: C, 60.29; H, 7.36; N, 7.78

STEP G

N- 4(N-BENZYLOXYCARBONYL-L-VALYL)AMINO-2,2-DIFLUORO-1,3-DIOXO-5-(4-{2-N-MORPHOLINYL}ETHYLOXY)PHENYL-PENTYL!O-METHYL-D-VALINOL

A mixture of the alcohol of example 7, step F (0.130 g, 0.184 mmol), 1,1,1-tris(acetyloxy)-1,1-dihydro-1,2-benziodoxol-3(1H)-one (Dess Martin periodane, 0.312 g, 0.736 mmol) and tert-butanol (0.035 ml, 0.368 mmol) in freshly distilled dichloromethane (over phosphorus pentoxyde, 5 ml) is stirred for 15 minutes at room temperature. The reaction mixture is hydrolyzed with isopropanol (0.6 ml) and concentrated in vacuo. The residue is suspended in dichloromethane (1.5 ml), filtered through a Fluoropore filter which is rinsed twice with dichloromethane (2×1 ml) and the filtrate is concentrated in vacuo (0.335 g). Purification by flash chromatography (silica gel, dichloromethane/methanol: 98:2 to remove the byproducts coming from the Dess Martin reagent, then 96:4 to recover the title ketone (0.109 g) and impure ketone largely contaminated with the starting alcohol (0.121 g). These impure material has been oxidized a second time following the above procedure to give more ketone (0.099 g). The combined batches (0.208 g) are crystallized from ethylacetate/pentane to give the title ketone in 69% yield.

Rf: 0.1 (dichloromethane/methanol: 95:5)

MS: MH!⁺ =704

Analysis: for C₃₆ H₅₀ N₄ O₈ F₂, 0.75 H₂ O Calculated: C, 60.20; H, 7.23; N, 7.80 Found: C, 60.28; H, 7.26; N, 7.94

The compounds of the present invention are useful as inhibitors of retroviral proteases required for replication, particularly the HIV-1 and HIV-2 viral proteases, the prevention or treatment of infection by the human immunodeficiency virus (HIV), and the treatment of consequent pathological conditions such as the acquired immunodeficiency syndrome (AIDS) in mammals capable of being infected with HIV virus. Treating AIDS, preventing infection by HIV or treating infection by HIV, is defined as including, but not limited to, treating a wide range of states of HIV infection: AIDS, ARC (AIDS related complex), both symptomatic and asymptomatic, and actual or potential exposure to HIV. For example, the compounds of this invention are useful in preventing infection by HIV after suspected past exposure to HIV by, e.g., blood transfusion, accidental needle stick, or exposure to patient blood during surgery.

The term "stereoisomers" is a general term for all isomers of individuals molecules that differ only in the orientation of their atoms in space. It includes mirror image isomers (enantiomers), geometric (cis/trans) isomers, and isomers of compounds with more than one chiral center that are not mirror images of one another (diastereoisomers). For amino-acids, the designations L/D, or R/S can be used as described in IUPAC-IUB Joint Commission on Biochemichal Nomenclature, Eur. J. Biochem. 138: 9-37 (1984).

For these purposes, the compounds of the present invention may be administered orally, parenterally (including subcutaneous injections, intravenous, intramuscular, transdermal, intrasternal injection or infusion techniques), by inhalation spray, or rectally, in dosage unit formulations containing convention non-toxic pharmaceutically acceptable carriers, adjuvants and vehicles.

Thus, in accordance with the present invention there is further provided a method of treating and a pharmaceutical composition for treating HIV infection and AIDS. The treatment involves administering to a patient in need of such treatment a pharmaceutical composition comprising a pharmaceutical carrier and a therapeutically effective amount of a compound of the present invention, or a pharmaceutically acceptable salt thereof.

These pharmaceutical compositions may be in the form of orally-administrable suspensions or tablets; nasal sprays; steriel injectable preparations, for example, as sterile injectable aqueous or oleagenous suspensions or suppositories) or they may be administered transdermally.

When administered orally as a suspension, these compositions are prepared according to techniques well known in the art of pharmaceutical formulation and may contain microcrystalline cellulose for imparting bulk, alginic acid or sodium alginate as a suspending agent, methylcellulose as a viscosity enhancer, and sweetener/flavoring agents known in the art. As immediate release tablets, these compositions may contain microcrystalline cellulose, dicalcium phosphate, starch, magnesium stearate and lactose and/or other excipients, binders, extenders, disintegrants, diluents and lubricants known in the art.

When administered by nasal aerosol or inhalation, these compositions are prepared according to techniques well known in the art of pharmaceutical formulation and may be prepared as solutions in saline, employing benzyl alcohol or other suitable preservatives, absorption promoters to enhance bioavailability, fluorocarbons, and/or other solubilizing or dispersing agents known in the art.

The injectable solutions or suspensions may be formulated according to known art, using suitable non-toxic, parenterally acceptable diluents or solvents, such as mannitol, 1,3-butanediol, water, Ringer's solution or isotonic sodium chloride solution, or suitable dispersing or wetting and suspending agents, such as sterile, bland, fixed oils, including synthetic mono- or diglycerides, and fatty acids, including oleic acid.

When rectally administered in the form of suppositories, these compositions may be prepared by mixing the drug with a suitable non-irritating excipient, such as cocoa butter, synthetic glyceride esters or polyethylene glycols, which are solid at ordinary temperatures, but liquidize and/or dissolve in the rectal cavity to release the drug.

Dosage levels of the order of 0.02 to 5.0 or 10.0 grams per day are useful in the treatment or prevention of the above-indicated conditions, with oral doses being higher. For example, infection by HIV is effectively treated by the administration of from 1 to 50 milligrams of the compound per kilogram of body weight from one to three times per day. It will be understood, however, that the specific dose level and frequency of dosage for any particular patient may be varied and will depend upon a variety of factors including the activity of the specific compound employed, the metabolic stability and length of action of that compound, the age, body weight, general health, sex, diet, mode and time of administration, rate of excretion, drug combination the severity of the particular condition, and the host undergoing therapy. Preferred compounds are when P2 is C₁₋₆ alkyl and especially C₁₋₃ alkyl, W and/or W' are C₁₋₃ alkyl, and/or R and/or R' are morpholinyl, C₁₋₄ alkylenyl or piperidyl.

The present invention is also directed to combinations of the HIV protease-inhibitory compounds with one or more agents useful in the treatment of AIDS, such as, for example, with known antiviral agents suitable for treating HIV 1 and HIV 2 viral infections, e.g., AZT, with or without a PNPase inhibitor, or in conjunctive therapy with DDI and a PNPase inhibitor.

The compounds of this invention may be assayed for their HIV-protease inhibition using the following published techniques.

Preparation of Retroviral Enzyme and

Assay for Inhibition of the Protease

A) Preparation of Retroviral Enzyme

To prepare the recombinant protease, the HIV protease was expressed via E. Coli by the published work of C. Guenet, et al., in European Journal of Pharmacology, Molecular Pharmacology Section, 172 (1989) 443-451.

B) Assay for Inhibition of Recombinant Viral Protease

Inhibition of the reaction of the protease with a peptide substrate Ser-Gln-Asn-Tyr-Pro-Ile-Val-NH₂, Km=1 mM were in 50 mM Na acetate, 10% glycerol, 5% ethyleneglycol, pH 5.5, at 3° C. for 1 hour. Various concentrations of inhibitor in 10 μl DMSO were added to 80 μl of assay solution and the reaction initiated by the addition of 10 μl (1.6 μg) of recombinant protease. The reaction was quenched with 16 μl of 4M perchloric acid. Products of the reaction were separated by HPLC (VYDAC wide pore 5 cm C-18 reverse phase, acetonitrile gradient, 0.1% trifluoroacetic acid). The extent of inhibition of the reaction was determined from the peak heights of the products. HPLC of the products, independently synthesized, provided quantitation standards and confirmation of the product composition.

By following the techniques referenced above, as well as by utilization of other known techniques, as well as by comparison with compounds known to be useful for treatment of the above-mentioned disease states, it is believed that adequate material is available to enable one of ordinary skill in the art to practice the invention.

As is true for most classes of compounds found to be useful in the pharmaceutical industry, certain subgeneric groups and certain specific compounds are more preferred such as those exemplified and shown in the following charts.

    __________________________________________________________________________     R.sub.1 P.sub.2                                                                              P.sub.1          R.sub.6 = H, R.sub.5                            __________________________________________________________________________     benzyl  isopropyl                                                                            4- (3-pyridyl)methloxy!benzyl                                                                   benzyl                                          3-pyridylethyl                                                                         isopropyl                                                                            4-pentenyl       2-pyridylmethyl                                 benzyl  isopropyl                                                                            4- (2-pyridyl)methyloxy!benzyl                                                                  benzyl                                          benzyl  isopropyl                                                                            4- (2-pyridyl)methyloxy!benzyl                                                                  2-pyridylmethyl                                 __________________________________________________________________________     R.sub.1 P.sub.2                                                                              P.sub.1          R.sub.6 = H, unless otherwise stated                                           R.sub.5                                         __________________________________________________________________________     benzyl  isopropyl                                                                            4- (3-pyridyl)methyloxy!benzyl                                                                  2-pyridylmethyl                                 (3-pyridyl)ethyl                                                                       isopropyl                                                                            4- (3-pyridyl)methyloxy!benzyl                                                                  benzyl                                          benzyl  t-butyl                                                                              4- (2-pyridyl)methyloxy!benzyl                                                                  3-pyridylmethyl                                 benzyl  t-butyl                                                                              4- (3-pyridyl)methyloxy!benzyl                                                                   ##STR28##                                      (2-pyridyl)ethyl                                                                       isopropyl                                                                            4- (3-pyridyl)methyloxy!benzyl                                                                   ##STR29##                                       ##STR30##                                                                             phenyl                                                                               4- (3-pyridyl)methyloxy!benzyl                                                                  benzyl                                          benzyl  isopropyl                                                                            4- (4-pyridyl)methyloxy!benzyl                                                                  benzyl                                          __________________________________________________________________________     R.sub.1 P.sub.2                                                                              P.sub.1          R.sub.6 = H, R.sub.5                            __________________________________________________________________________     benzyl  isopropyl                                                                            4- (2-pyridyl)methyloxy!benzyl                                                                   ##STR31##                                      (3-pyridyl)ethyl                                                                       isopropyl                                                                            4- (3-pyridyl)methyloxy!benzyl                                                                  benzyl                                          benzyl  isopropyl                                                                            4- 2-(N-morpholyl)ethyloxy!benzyl                                                               3-pyridylmethyl                                 (2-pyridyl)ethyl                                                                       cyclopentyl                                                                          4- 2-(N-morpholyl)ethyloxy!benzyl                                                               benzyl                                          benzyl  isopropyl                                                                            4- 2-(N-morpholyl)ethyloxy!benzyl                                                                ##STR32##                                      benzyl  isopropyl                                                                            4- 2-(N-morpholyl)ethyloxy!benzyl                                                               2-pyridylmethyl                                 benzyl  isopropyl                                                                            4- 2-(N-morpholyl)ethyloxy!benzyl                                                                ##STR33##                                      benzyl  isopropyl                                                                            4- 2-(N-piperidyl)ethyloxy!benzyl                                                               2-pyridylmethyl                                 benzyl  t-butyl                                                                              4- 2-(N-morpholyl)ethyloxy!benzyl                                                                ##STR34##                                      benzyl  t-butyl                                                                              4- 2-(N-morpholyl)ethyloxy!benzyl                                                                ##STR35##                                      (3-pyridyl)ethyl                                                                       isopropyl                                                                            4- 2-(pyridyl)methyloxy!benzyl                                                                   ##STR36##                                      (3-pyridyl)ethyl                                                                       isopropyl                                                                            4- 3-(pyridyl)methyloxy!benzyl                                                                   ##STR37##                                      (3-pyridyl)ethyl                                                                       t-butyl                                                                              4- 4-(pyridyl)methyloxy!benzyl                                                                   ##STR38##                                      benzyl  isopropyl                                                                            4- 2-(pyridyl)methyloxy!benzyl                                                                   ##STR39##                                      (3-pyridyl)ethyl                                                                       isopropyl                                                                            4- 2-(pyridyl)methyloxy!benzyl                                                                   ##STR40##                                      benzyl  isopropyl                                                                            4- 2-(N-morpholyl)ethyloxy!benzyl                                                                ##STR41##                                      (2-pyridyl)ethyl                                                                       isopropyl                                                                            4- 3-(pyridyl)methyloxy!benzyl                                                                   ##STR42##                                      benzyl  isopropyl                                                                            4- 2-(N-piperidyl)ethyloxy!benzyl                                                                ##STR43##                                      (3-pyridyl)ethyl                                                                       isopropyl                                                                            4- (2-pyridyl)methyloxy!benzyl                                                                   ##STR44##                                      benzyl  isopropyl                                                                            4- (2-N-morpholyl)ethyloxy!benzyl                                                                ##STR45##                                      benzyl  phenyl                                                                               4- (2-N-morpholyl)ethyloxy!benzyl                                                                ##STR46##                                      (3-pyridyl)ethyl                                                                       isopropyl                                                                            4- (2-N-morpholyl)ethyloxy!benzyl                                                                ##STR47##                                      __________________________________________________________________________ 

What is claimed is:
 1. The compound which is 4-(N-benzyloxycarbonyl-L-valyl)amino-2,2-difluoro-3-oxo-5- 4-(oxo-4-pentenyl)phenyl!N-benzyl pentanamide.
 2. The compound which is 4-(N-benzyloxycarbonyl-L-valyl)amino-2,2-difluoro-3-oxo-5- 4-2{N-morpholinyl}ethyloxy)phenyl!N-benzyl pentanamide.
 3. The compound which is 4-(N-benzyloxycarbonyl-L-valyl)amino-2,2-difluoro-3-oxo-5 4({2-pyridyl}methyloxy)phenyl!N-benzyl pentanamide.
 4. The compound which is N 3-(3-pyridyl)propanoyl!4-(L-valyl)amino-2,2-difluoro-3-oxo-5 4-2{N-morpholinyl}ethyloxy)phenyl!N-benzyl pentanamide.
 5. The compound which is N 3-(3-pyridyl)propanoyl!4-(L-valyl)amino-2,2-difluoro-3-oxo-5 4({2-pyridyl}methyloxy)phenyl!N-benzyl petanamide.
 6. The compound of which is N- 4-(benzyoxycarbonyl-L-valyl)amino-2,2-difluoro-1,3-dioxo-5- (4-{2-N-morpholinyl}ethyloxy)phenyl-pentyl!O-benzyl-D-valinol.
 7. The compound which is N- 4-(N-benzyloxycarbonyl-L-valyl)amino-2,2-difluoro-1,3-dioxo-5- (4-{2-N-morpholinyl}ethyloxy)phenyl-pentyl!O-methyl-D-valinol. 